Maine State Police and a county sheriff previously reported there had been an active shooter on Wednesday night but did not provide details.
"There is an active shooter in Lewiston," Maine state police said on the social media platform X. "We ask people to shelter in place. Please stay inside your home with the doors locked. Law enforcement is currently investigating at multiple locations."
The Androscoggin County Sheriff's Office posted two photographs of the suspect on Facebook, saying he was at large.
Police respond to the mass shooting in Lewiston, Maine.
The county sheriff asked for the public's help in identifying the pictured suspect, a bearded man in a long-sleeved shirt and jeans holding a rifle in the firing position.
The Central Maine Medical Centre in Lewiston issued a statement saying it was "reacting to a mass casualty, mass shooter event" and coordinating with area hospitals to take patients.
Lewiston is part of Androscoggin County and about 56km north of Maine's largest city, Portland.
The Sun Journal, citing a Lewiston police spokesperson, reported shootings at three separate businesses: Sparetime Recreation, Schemengees Bar & Grille Restaurant, and a Walmart distribution centre.
President Joe Biden has been briefed and will continue to receive updates, a US official said in Washington.
Maine Governor Janet Mills said in a statement she had been briefed on the situation.
Maine senator Angus King said he was "deeply sad for the city of Lewiston and all those worried about their family, friends and neighbours" and was monitoring the situation.
The massacre is the deadliest mass shooting in the United States since at least May 2022, when a gunman opened fire at an elementary school in Uvalde, Texas, killing 19 children and two teachers, according to the Gun Violence Archive.
The number of US shootings in which four or more people were shot has surged since the COVID-19 pandemic began in 2020, with 647 occurring in 2022 and 679 projected to occur in 2023, based on trends as of July, according to data from the archive.
The deadliest US mass shooting on record is the massacre of 58 people by a gunman firing on a Las Vegas country music festival from a high-rise hotel perch in 2017.
with AP
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